Centrifuge for the continuous separation of substances of different densities

ABSTRACT

The centrifuge (1) described has at least one device (11,12) designed to control the operation of the centrifuge, the devices being mounted to rotate with the rotating part of the centrifuge and to be operated by a mechanical actuator (13) also rotating with it. Such devices may, for instance, be drain valves, periodically opening discharge valves, sill height adjustment devices, pressure-control devices, temperature-control devices, etc. At least one part of the devices of this centrifuge to be controlled independently of the centrifugal force is designed so that the rotating actuator (13) changes its shape as a function of the temperature and has at least one temperature-specific shape.

The invention relates to centrifuges for separating substances ofdifferent densities, for example, solid-liquid mixtures, with at leastone device located for co-rotation with a rotating portion of thecentrifuge and controlled by an also co-rotating mechanical actuator fordetermining the operation, for example, of drain valves, periodicallyoperating discharge valves, sill height adjustment devices, pressurecontrol devices, temperature control devices, and the like.

By operation determined by the controlled devices, there are to beunderstood externally controlled operating parameters, as these can beaffected, for example, by sill height adjustment devices, dischargevalves, residue drain valves and the like. Also included is theadjustment of operating conditions, that is control, for example, as afunction of the turbidity of the concentrate, or the residual moisturein the solids. Particularly included are sill height adjustment devices,such as radially displaceable sill plates, two consecutively locatedsill plates of different diameters with controllable intermediaterun-off for level reduction, sill plates connected to a controlled valveat greater diameter for lowering the level, outlet valves such as valvesfor draining sludge or a more or less large fraction of the bowlcontents, e.g. closing of the valves while cooling the actuator eitherthrough a separate cooling medium or through exiting centrifuged medium,as well as residue discharge valves for the complete emptying orcleaning of the centrifuge, as is appropriate especially for perishable,explosive and/or radio-active materials, and cleaning for product changewithout stopping the machine. Finally, the prevention of operatingstoppages forms part of the purpose of the operation, for which thereare used primarily devices for overload protection, such as pressurecontrol devices, for example, for grease expansion in the helixbearings, namely through increase in volume of the grease space by meansof piston displacement, or else through relief valves. To preventoperating stoppages there are further used devices for controllingtemperature, namely in the separating chamber as exit valves for hotliquid, gases or vapors and in the bearing space through valves forsupplying lubricant/cooling liquid from a co-rotating reservoir or fromoutside the bowl, e.g. upon excessive heating of a bearing due toincreased friction. Finally there can be provided devices for protectingagainst turning moment overload, which can cause interruption of thedrive of the helix, e.g. due to friction heating, especially through adisengageable coupling. This listing of the devices for controlling theoperation of the centrifuge in relation to the previously mentioned,fundamental purposes, does not purport to exhaust the areas ofapplication of the actuators here under discussion.

The actuation of control devices inside a centrifuge, i.e. at rotatinglocations, is difficult and complicated to carry out from the outsideand indeed is possible only under certain operating conditions. Thus,one can supply a control liquid through a stationary supply pipe, whichextends into a circumferential trough (circumferential pockets) of therotating centrifuge portion and from there exerts a control force, e.g.for operating a piston serving as the actuator of a control device, as afunction of the centrifugal force resulting from the rate of rotation ofthe centrifuge. A control force which is specifically pressure dependentand therefore independent of centrifugal force could be provided by apressure-transmitting liquid which is ducted through a rotating couplingfrom a stationary conduit into a rotating conduit, but the pressurizedand leakproof rotating coupling is costly--see, for example, GermanOffenlegungsschrift (DE-OS) 30 09 669.

Thus, for example, to operate residue drain valves--the liquid residueremaining in the drum after separation is desirably removed, e.g.because it is ejected into the solids trough when the centrifuge isstopped or because it makes the cleaning of the drum moredifficult--there is utilized the centrifugal force which acts radiallyupon the valve as a function of the rate of rotation of the centrifuge,and which acts against the force of a radially inward directed spring insuch manner that, at the operating rate of rotation, the centrifugalforce keeps the valve closed against the spring pressure, while thevalve opens during reduction in the rate of rotation--see, for example,British patent (GB-PS) 614 501.

Examples of control by means of a control liquid, which is suppliedfreely to the centrifuge rotor via annular pockets, are centrifuge bowlswith intermittent sludge removal. These are usually provided with valvesor tubular slide valves which are controlled from outside duringoperation by means of the control liquid. Under the influence of thecentrifugal force, the control liquid develops high hydraulic pressureswhich are utilized to operate the valves or tubular slide valves--see,for example, German Offenlegungsschrift (DE-OS) 30 11 620.

For many centrifugeable media, the adjustability of the liquid level inthe bowl during operation decisively influences the result of theseparation and, in many instances, makes possible the use of decantersin this field. This is particularly true for media with variablecomposition and solids which are difficult to transport via helix. It isknown to use, for such adjustability of the liquid level in the bowl, orrather the liquid depth in the separating chamber of the centrifuge, anadjustable weir plate, but this is very costly and requires higherenergy consumption than free flow, especially for larger machines. Inmany cases, there suffices a sill diameter adjustment of a fewmillimeters, e.g. during start-up of decanters with so-called Superpool,so that the adjustment range of an adjustable weir plate is notexploited. To prevent breakthrough of the liquid to the solids side, thesill diameter must initially be set to a higher value, and then switchedto a smaller sill diameter, i.e. to Superpool, after sufficient buildupof solids before the sill for high dry solids content. Such a decanteris known--see German patent (DE) 37 28 901--with provision for a bypassfor the concentrate run-off, so that one or the other of two stationaryweir plates is selectively utilized. This apparatus works with ahydraulic tubular slide valve control known from separators.

A disadvantage of these arrangements is the dependence of the operationof the respective device upon the centrifugal force and thus upon theprevailing or intentionally established rate of rotation,and the dangerof blockage and dirtying of valves or tubular slide valves throughdeposits, given the limited, rate-of rotation dependent forcedifferentials for the closing and opening movements, or the high cost ofthe controls.

The invention has the object of providing centrifuges of the type underdiscussion whose controllable devices are operated at least in partunder a control which is independent of centrifugal force.

Starting with a centrifuge having the initially describedcharacteristics, the object is achieved in accordance with the inventionby utilizing, for the control of the respective device, an actuatorwhich changes its shape as a function of temperature, and which exhibitsat least one temperature-specific shape.

The use in accordance with the invention of an actuator which changesshape as a function of temperature and has at least onetemperature-specific shape for the control of the respective deviceopens up the possibility of using a new physical control parameter,namely temperature, which is independent of centrifugal force. Thiscontrol parameter can be applied to the actuator from outside thecentrifuge, but it can also be derived from the temperature conditionsof the mixture, or of at least one component of the mixture which is tobe separated, or of the centrifuge, and used to control the actuator. Inthe latter case, the actuator itself can simultaneously function astemperature sensor.

The actuator takes on at least one temperature-specific shape,particularly if the temperature to which the actuator is subjected iscaused to rise by a predetermined amount through a heated gaseous orliquid medium, or through the mixture, or the centrifuge. In case thereoccurs the assumption of only a single specific shape as a function oftemperature, then an additional force is needed for the return to theother shape (initial state) at temperatures below the switching range,which can be provided by a spring element (e.g. of spring steel)utilized as a shock absorber, or by centrifugal force provided by therotation of the centrifuge. However it is also possible to construct theactuator so that it reacts to temperature rises with one specific shapeand to temperature decreases back to a different shape, in which caseone shape transformation can occur with less force development than theopposing one, so that an additional spring or centrifugal force mayagain be required.

As actuators of this type there can be considered elastic elements, e.g.wax-filled piston-cylinder arrangements, but especially bi-metallicelements and, especially preferred, so-called shape-memory metals.

In a particularly preferred embodiment there are utilized actuatorswhose shape change takes place within a control temperature range whichis small relative to the operating temperature range. This yields acontrol action, for the devices which are operated by the respectiveactuator, that resembles a switching action. This is desirable in manycases, especially when a change in operation during start-up orinterruption, monitoring or the like should trigger a spontaneousreaction with highest possible force development, so that even dirt ordeposits on valves, slide valves or like actuator elements do not causeblockages. Such a switch-like action of the actuator can be provided bya bi-metallic element which exhibits two stable switching statesseparated by a temperature-dependent deformation toggling value. Aparticularly preferred usable shape-memory metal also has thisswitch-like characteristic:

Shape-memory metals--also known as memory alloys--experience within anarrow temperature range a structural transformation(austenite-martensite) and thereby change their shape. Thus theshape-memory metal, or rather the actuator made from it, has apredetermined shape in the austenitic structure, while in contrast theshape-memory metal at lower temperature, e.g. at room temperature, isreconfigured under martensitic structural conditions into a differentshape. For the actuators which are used here, this could be designatedas the initial configuration. If the actuator having this initialconfiguration is heated, the structure of the memory metal again becomesaustenitic above a certain temperature, whereupon the component revertsalmost completely to its original shape. This process of memorycapability in response to heating to a predetermined configuration canexist as a one-way effect, i.e. the actuator made of such a one-waymemory metal assumes its original shape only upon temperature increase,whereas the reversion to another, namely the above-mentioned initialconfiguration, must always be brought about by external forces.

There are also memory metals, or memory alloys, with so-called two-wayeffect, i.e. they assume a specific high temperature configuration aswell a specific low temperature configuration, i.e. the shape change isreversible. However, in so doing, the transition to the low temperatureshape is generally associated with relatively lower force development,so that reinforcing external influences, such as stored spring forces orcentrifugal forces must be applied, in order to accomplish thetransition into the low temperature shape. The structural transformationof such memory-metal actuators takes place suddenly when the requiredtemperature conditions are present, so that the speed of shape change isultimately determined by the rate of heat supply or removal. A furtherspecial advantage of these memory metals is their high performance perunit volume, at least in the direction of assuming the shape of theaustenitic structure, as well as the possibility of combining sensor andactuator in a single component. There are various memory alloys of thekind under discussion as, for example, copper-zinc-aluminum alloys andnickel-titanium alloys, of which the latter are preferably used inaccordance with the invention due to their shape-change properties, thepermissible pressure, and above all the corrosion resistance.

In a further preferred embodiment, the one, or one of the actuatorsconnected to the devices which are to be controlled is formed of two ormore memory metals arranged in parallel and/or series. Thereby one canincrease the force developed during shape change in the parallelconnection, or increase the shape change magnitude in the seriesconnection. In both cases, one can also achieve a step-like shape changebehavior of the whole so-configured actuator within differentshape-changing temperature ranges. In another embodiment, the one, or atleast one of the actuators can interconnect two or more which areconnected in series and/or parallel and moving in opposite directionsdue to shape changes resulting from temperature-caused structuralchanges, so that, in the course of a step-wise temperature increasewithin appropriately differing shape changing temperature ranges, therecan be produced a first switching step, which is then canceled, ormodified in a succeeding switching step.

For the restoring force opposing a shape change, which takes place inthe transition from the martensite to the austenite state, one canutilize the centrifugal force which varies with the centrifuge rate ofrotation for actuators made of one-way memory alloys, as well as by wayof reinforcement when using two-way memory alloys. The positioning ofthe actuator made from such alloys should be such as to act as much aspossible in a radial direction, which can be achieved especially forlengthwise acting shape changes of the actuators with respect to deviceswhich are radially actuatable, particularly valves located in thehousing region. In another embodiment, and particularly for suchstroke-like movements of the actuators which exhibit no, or only arelatively slight radial component, there is required a restoring forcein order to shift the actuators into the low temperature shape of thememory-metal, which is preferably done by means of a spring, which isarranged as a shock absorber. Here, too, the use of one-way memorymetals can be contemplated, in which case the restoration is carried outentirely by spring forces, or else the use of two-way memory metals, forwhich the restoration is carried out additionally by the force of aspring. Of course it is also possible to subject to additional forcesactuators which are under centrifugal force.

The actuators of memory-metal are preferably in the form of pull-rod,coil spring, torsion bar, or leaf spring.

In order to apply to the actuator a specific control command fromoutside the centrifuge, there is preferably supplied an appropriateliquid or gaseous heating and/or cooling medium, preferably via astationary supply pipe which ends in a ring-shaped receiving channelfrom which the medium is led to the actuator by centrifugal forcedependent upon the centrifuge rate of rotation add through radial flowpath components, around which it flows, or through which it isconducted.

For the case in which devices, or one or more of all the installeddevices are not to be specifically controlled from outside, therespective actuator is so arranged that it simultaneously serves assensor for the temperatures created by the centrifuge and/or thecentrifuge contents. This can be utilized, for example, to determine thetemperature change of the respective actuator which occurs uponintroduction of cleaning liquid following prior operation with a coldcentrifuged medium. The actuator can then open a valve provided in thesidewall region of the bowl and allow the cleaning liquid to flow out.Furthermore the actuator can be subjected to a temperature variationwhich is due to contact with exiting centrifuge medium. In addition, toprevent leakage-caused overloads of seals in a bearing space,particularly the helix bearing interior, it is possible to use this as apressure equalization chamber, or to place it in communication withsuch, whose volume can be increased by means of an actuator in contactwith the lubricant in response to a lubricant temperature rise,preferably with the aid of at least one piston extending into a hollowchamber at whose face exposed to the lubricant the actuator--preferablyin the form of at least one coil spring shaped memory metal--is locatedand to whose opposite face a restoring spring is applied.

During centrifuge start-up, the more viscous lubricant has less tendencyto escape through the seals; therefore it is desirable to enlarge thebearing space, or the equalization chamber only at a predeterminedtemperature, which is achieved by the switching action of the memorymetal. However, it is more significant that, above a certain temperaturedependent pressure, the seals can wear more and be ruptured. Byproviding several parallel actuators and pistons with staggeredtemperature dependence, there can be achieved a step-wise enlargement ofthe chamber volume, or else by constructing one actuator, acting uponone piston, of several memory metals connected in parallel or in series,which exhibit different temperature dependent switching thresholds andthereby displace the piston during rising temperature step-wise in thedirection of enlarging the chamber volume.

Preferred applications of the actuators with their accompanying devicesresult from the following measures: orifices located radially outward inthe centrifuge bowl are so arranged that the centrifuge bowl can beemptied through these orifices; the orifices are so arranged in thethick sludge portion of the centrifuge that thick sludge can beperiodically evacuated from the centrifuge bowl through these orifices;the orifices are located at a larger diameter than an overflow silllocated in the centrifuge bowl, so that, with open orifice, there iscreated an internal diameter of the liquid level which is greater thanthe internal diameter established by the overflow sill. In addition, theorifices can be located between two spaced-apart sill plates, the sillplate facing the separating chamber having a greater internal diameterthan the other sill plate, so that with open orifice, the liquid'sinternal diameter is determined by the sill plate with the greaterdiameter, whereas with closed orifice, it is determined by the sillplate with smaller internal diameter. On the other hand, actuators whichact in the radial direction can be provided, especially if formed astemperature-dependent length-varying rods or hollow rods, which arerespectively connected to a radially displaceable sill plate locatedopposite an accompanying discharge opening.

By these adjustments of the sill heights and therefore pool depths inthe separating section of the centrifuge, mixtures which are difficultto separate can be processed more easily, especially sludges or thelike, which require the accumulation of a certain amount of solids forthe removal of solids to proceed.

In order to ensure the shape change action over an extended period oftime, or a multiplicity of shape changes, it is advisable to apply tothe memory metals (memory alloys) a restoring force at the moment oftransformation from the austenitic to the martensitic state,corresponding to a force of at least 30N/mm. Because it is not certainthat, during structural transformation of austenite into martensite,there is created a corresponding centrifugal force which equals thatforce--a machine of the type under discussion can come to a stop beforethe structural transformation has occurred--it can be advisable for manyapplications to build in a force storage means, for example a spring,which provides the appropriate restoring force independently of thecentrifugal force. Moreover, components can have memory alloys extendingonly over portions thereof, so that only predetermined portions of thesecomponents take part in the shape change.

Because of their property of uniting sensor and actuator in a singlecomponent, actuators of memory metals are particularly advantageouslyusable when the switching process is not triggered through externalheating or external cooling, but directly through the producttemperature. In this regard, one can particularly envisionself-regulating discharge mechanisms for sludge or concentrate, wherethe heat of friction created by the exit through narrow nozzlesautomatically adjusts the discharge cross-section. As an example: asmall discharge opening leads to reduced flow, results in heating,causes the transformation into austenite, whereby the discharge openingis enlarged; alternatively the discharge opening is large whereby thethroughput is great so that cooling takes place which causestransformation into martensite, whereby the opening is reduced.

The heat supply or the cooling needed for the shape change of theactuators need not necessarily occur through liquid or gaseous heatingmedia in the case of external control, it is also conceivable to utilizefor this purpose frictional heat which is produced by the prevailingoperation of the machine, thus for example, through adjustment of thedifference in rate of rotation between helix and bowl of a decanter,through restriction of the outflow via the adjustable sill plate and soforth. In addition one can conceive using chemicals with endothermic orexothermic reaction for thermal control of the actuators.

In a preferred embodiment, the above-mentioned procedures are applied toscroll conveyor centrifuges, or to drum centrifuges.

Preferred embodiments of the invention appear from the dependent claims,particularly in conjunction with the exemplary embodiments shown in thedrawing, whose following description further explains the invention.There are shown in

FIG. 1 a longitudinal cross-section taken along the axis of a centrifugethrough the head-end lid portion of a centrifuge;

FIGS. 2 to 8 half-sections corresponding to the sectional view of FIG. 1through embodiments with controllable valve devices;

FIG. 9 a half-section corresponding to the section of FIG. 1 with a sillplate adjusting device;

FIG. 10 a half-section corresponding to the section of FIG. 1 for thevolume adjustment of the lubricant space of a helix bearing.

In the examples according to FIGS. 1 to 10 there is assumed in each casea scroll conveyor centrifuge 1 of known construction. This centrifugehas a centrifuge bowl (housing) 2 which is rotatably supported onbearing 8 in a manner not shown and which has a coaxially rotatablehelix 3 with hub 4, whose helix turns 5 attached to the hub extend closeto the inner wall of centrifuge bowl 2. The centrifuge bowl is providedwith a bowl lid 6 at its head-end facing away from the solids outlet(not shown). Between its hub support extending into the interior of thecentrifuge and the helix hub 4 at this head-end of the centrifuge, thereis a helix bearing 7. Through the hub of the bowl lid 6 there extends astationary inlet pipe 9 which is held in place in a manner not furtherillustrated, and through which the mixture to be separated isintroduced, in a manner not further illustrated, through an opening inthe bowl hub into the separating chamber of the centrifuge which isdefined by the inner wail of bowl 2, the outer wall of hub 4, the turnsof the helix 5 and the inner wall of the bowl lid 6. The bowl lid 6 ispierced by outlet openings 21 uniformly distributed over itscircumference, through which a separated phase of the mixture,particularly a liquid phase of a solid-liquid mixture, exits from thecentrifuge. The outlet openings 21 are provided with a sill plate 10,whose inner diameter determines the depth of pool 17 prevailing duringoperation. The bowl is set into high speed rotation, the helix locatedinside the bowl rotates at only a slightly lower rate of rotation withrespect to the bowl in such a manner that the helix 5 transports thesolids which deposit on the inner wall of bowl 2--the heavier phase ofthe mixture to be separated--to the other head-end, i.e., to the outletopenings which are provided there, if desired via a conically narrowingdrying section, as is known for scroll conveyor centrifuges of the typeillustrated.

In the example according to FIGS. 1 to 5, orifices 11 are provided inthe bowl housing or in the lid at the level of the bowl housing, so thatthere can take place, through these orifices 11, primarily a residuedischarge from the centrifuge. In addition a periodic thick sludgedischarge is possible through such orifices 11. According to FIG. 1, theorifice 11 is provided as its closing element with a control means 12 inthe form of a conical valve body which is attached to or formed at theradially outward end of a rod-like actuator 13, which latter is madefrom a temperature dependent, variable length memory metal rod. The rodshaped actuator 13 is surrounded by and spaced from tube 14 which isheat insulating so that a tube-like space 20 is created between a majorportion of the surface of actuator 13 and the inner surface of tube 14which opens into a tub-shaped annular space 39-19-, in which the outletopening of a supply pipe terminates which, like inlet tube 9, isstationary and serves for the introduction of a liquid or gaseousheating and/or cooling medium. In the radially outward end of theannular space between actuator 13 and tube 14, there is provided in bowlcover 16 an exit opening 16 for this medium so that, for example, aheating medium supplied through supply pipe 15 flows out and canbe,replaced by a cooling medium.

The actuator 13 can be formed of a rod-like memory metal with one-wayaction or two-way action, in either case in such manner that upon supplyof heat and exceeding of the switching temperature--and with it theretransformation of martensite into austenite--there takes place ashortening in the rod's lengthwise direction and the operator 12 movesradially inward away from the mouth of opening 11, so that the liquidremainder present in the separating chamber can escape through nozzleopening 11. When nozzle opening 11 is to be closed again, the heating ofthe actuator by the heating medium is terminated, or brought back to alow temperature through a cooling medium, under whose influence therecan take place a deformation in the lengthwise direction of the rod-likeactuator under external forces or with reinforcement of such externalforces, which takes place here under the influence of centrifugal forceat a predetermined centrifuge rotation rate.

In the embodiment of FIG. 2 there is a nozzle opening 11 which issimilarly attached to the lid at the level of bowl housing 2 andcontrollable by means of an operator 22 which again takes the form of aconical valve face. This operator is made of one piece with, or elseattached to a tube-like actuator 23 made of a memory metal which, duringtransformation from martensite into austenite structure, undergoes ashortening in its lengthwise direction, i.e. in response to appropriateheating. This actuator 24 is also surrounded by a guide tube 24 andguided lengthwise in the radially outward end of guide tube 24. Thehollow space of the actuator 23 terminates in an annular space 39similar to that in FIG. 1, for example, in which there also terminatesthe supply pipe 15 for gaseous or liquid heating or cooling mediumsupplied from outside. Thus the medium flows from tube 25 via theannular space 39 into the rod-like hollow space 26 of tubular actuator23 and leaves it in the radially outward end portion through an outletopening 25 which passes axially through the conical valve operator 25,so that the medium can penetrate into orifice 11. The operation issimilar to that which was explained in connection with FIG. 2 and alsoserves the same purposes.

In the embodiment example of FIG. 3, the orifice 11 constructed in thesame manner as in FIG. 2 is to be closed and opened by an operator 27 ofthe conical valve body type, which is attached to a rod extendingradially with respect to the rotation axis of the centrifuge, which hasat its radially inward end a collar 29--here formed by a snap ring--andwhich passes with a lot of play through a bushing 31. This bushing 31 isso attached to the hub of the bowl lid 6 that, between it and collar 29,there exists an annular hollow space 28 in which an actuator 30 in theform of a coil spring is mounted. This coil spring-like actuator 30 ofmemory metal bears against the facing surfaces of collar 29 and bushing31. Above the hollow space 28, it is in communication with an annularspace 39 in which, as in the other examples of embodiments, thereterminates the outlet opening of a supply pipe for gaseous or liquidheating or cooling medium. Thus, this cooling medium passes from supplypipe 15 via the annular space 39 into hollow space 28 and exits from thelatter into the separating chamber through the annular gap formed by theplay between the bushing 31-and the surface of the rod-shaped portion ofthe operator 27. In its austenitic structure, the memory metal ofactuator 30 exhibits a temperature specific shape which is longer in theaxial direction of the coil spring configuration than the dimensionshown in FIG. 3. Thus, if a heating medium is supplied and the coilspring shaped actuator 30 is thereby heated above the threshold value,so that the martensitic structure changes into austenitic structure, theactuator 30 presses against collar 29 and thereby lifts the actuatoraway from nozzle opening 11, whereas during cooling--e.g. through supplyof a cooling medium--this shape reverts to the state shown in thedrawing, with formation of the martensitic structure, due to thecentrifugal force which is a function of centrifuge rate of rotation, inwhich the operator 27 with its cone shaped valve body closes orifice 11.Thus there is described a third embodiment, with operation and mode ofutilization as described in connection with FIG. 1.

FIG. 4 shows the arrangement of an orifice 11 in the region of thehousing of centrifuge bowl 2, whose inlet opening is provided withopening and closing operator 32 in the form of a cylindrical pistonwhose operating range extends through a hollow space 34 and whichexhibits inside the hollow space a cylindrical piston-like slide valveskirt 35. Between the end of hollow space 34 facing the orifice 11 andthe confronting face of slide valve skirt 35, there is placed anactuator 33 in the form of a coil spring-shaped memory metal, whereasbetween the end of hollow space 34 facing away from orifice 11 and theconfronting face of slide valve skirt 35 there is inserted aconventional coil spring 36. The portion of hollow space 34 in which theactuator 33 is located, is connected by a radially extending heatinsulating supply pipe 37 to an annular space 39 opening into itsradially inner end in which--as in the previously treatedembodiments--there terminates a stationary supply pipe 15 for gaseous orliquid heating and/or cooling medium. As shown in this exemplaryembodiment, with nozzle opening 11 closed by operator 32, the actuator33 exhibits that shape which it assumes after externally causeddeformation through formation of the martensitic structure and which, interms of its function, can be considered as its starting shape. If theorifice 11 is to be opened, the heating medium is introduced, throughpipe 15, annular space 39 and supply pipe 37, into that part of hollowspace 34 containing the actuator 33, and from which the heating mediumcan be removed through an outlet opening 38 leading radially outward.This heats the actuator 33, which stretches through transformation ofthe martensitic into the austenitic structure in the axial direction ofthe coil spring shape so as to assume the temperature specific shapeprevailing in the austenitic structure. Due to this stretching, theoperator 32, which is slidable parallel to the axis of rotation of thecentrifuge, is displaced against the force of spring 36 via the slidevalve skirt 35, and the orifice 11 is freed up. If the temperature againdecreases, as by introduction of a cooling medium over the same path asthe heating medium, then below a predetermined temperature threshold,there can take place a reversion into the starting shape illustrated inFIG. 4 under the force of spring 36 and the formation of martensite, sothat the operator 32 closes orifice 11. Thus FIG. 4 represents a furtherembodiment of the operation and applications previously described inconnection with FIG. 1.

FIG. 5 shows a further variant in which an orifice 11, which extendsthrough bowl lid 6 coaxially with the rotation axis of the centrifuge,has an outlet opening that is opened and closed by an operator 42 in theform of a rotary slide valve. In its open state, the outlet of theorifice 11 terminates in a rotary slide valve outlet 41 and is thereforeopen for outflow from the separating space. On the other hand, if theoperator is rotated around its radially extending longitudinal axis,then the outlet of orifice 11 is closed. This rotation is caused by atube-like actuator 43 to whose radial end the operator 42 is connectedand which takes the form of a hollow torsion bar of memory metal. Theactuator 43, made as a hollow torsion bar, has its longitudinal tubeaxis extending radially and is attached at its radially inner end tobowl lid 6-44-, whereas the radially outer end is freely rotatable andrigidly connected to the rotary valve operator.42. The rod-shaped hollowspace 47 of the tube shaped actuator 43 communicates at its radiallyinner end with an annular space 39 in which, in previously describedmanner, there terminates the outlet opening of a supply pipe for gaseousor liquid cooling or heating medium. The walls of annular space 39 areprovided with heat insulation 40--as in the other embodiments--in orderto prevent too high a heat flow in the hub region of bowl lid 6. At itsradially outward end, the rod shaped hollow space 47 of actuator 43 isin communication, via an austenitic temperature-specific opening 46,with an outlet opening 45, which is slit-shaped or which operates via anannular space, so that the heating or cooling medium can be removed fromthe hollow space. In the illustrated embodiment the actuator is in itsaustenitic temperature-specific shape, in which liquid can be removedfrom the separating chamber through orifice 11 and the rotary valve exit41. If this is to be prevented, then cooling medium is supplied throughsupply pipe 15, annular space 39 and rod-like hollow space 47 ofactuator 43, or else one waits for appropriate cooling, whereupon afterfalling below a predetermined temperature threshold and if appropriatewith the assistance of a torsion spring (not shown), which makes atorsional movement that is transmitted to the operator 42, the memorymetal of actuator 43 switches into its starting shape. This leads to arotation of operator 42 such that the exit from orifice 11 is closed.Upon raising of the temperature, or supply of an appropriate heatingmedium, the actuator 43 in the form of a hollow torsion rod againassumes its temperature determined shape in which, as shown in FIG. 5,the orifice is in communication with the rotary valve exit 41. Thetorsion rod could also consist of two segments connected radially toeach other, one of which assumes its temperature specific shape during afirst, low heating, while the other segment assumes its temperaturespecific shape at the higher temperature, the arrangement being soconstructed that, upon reaching of the first heat threshold, the orifice11 is closed and upon reaching of the second threshold value the same isreopened. As far as applications, reference is made to the details givenfor the prior embodiment examples.

The exemplary embodiment according to FIG. 6 shows, in addition to theprovision of an axially external sill 10 with a relatively smallinternal diameter, an additional sill 50 located in the region of bowllid 6 axially inside the centrifuge and with a larger internal diameter51. In the region between the two sills 10 and 50, there is a hollowspace 49 which, relative to the outer sill 10, is comparable todischarge openings 21. This hollow space terminates in an orifice 11 ina housing segment of bowl lid 11. This orifice is connected as theopening and closing device for an operator 52 in the form of a valvebody, which is connected to a radially extending tube-shaped actuator 53of memory metal that extends through and is spaced from a guide tube 54.The rod-like hollow space 56 of actuator 53 serves to pass, via astationary supply pipe 15 and an annular space in previously describedmanner, heating or cooling medium which leaves the rod-shaped hollowspace 56 at its radially outward end through an outlet opening 55 whichis positioned axially in the cone-shaped operator 52, so that thismedium can be removed through the orifice 11. The operation of theactuator and the operator is the same as described in connection withFIG. 2. Through the use of actuator 53 and with it the operator 52 whichis to be opened and to be closed, it is possible to determine whetherthe depth of the pool 17 in the separating chamber of the centrifuge iscontrolled by the smaller inner diameter 48 of sill 10--orifice 11 isclosed, liquid is removed over sill 10--or by the larger diameter ofsill 50--orifice 11 is open, the liquid is removed from the separatingchamber over sill 50 and through orifice 11.

In FIG. 7 there is illustrated another embodiment for the mode ofoperation, or the kind of use described with reference to the exampleaccording to FIG. 6. Here, the orifice is provided with a valve bodyshaped operator 57 which terminates in a rod shaped operating memberthat passes through a hollow space 58 and exhibits a collar 59 at itsradially inward end. The rod shaped operating member extends radiallyfurther outward through an annular support 61 which is fixedly attachedto the bowl lid. In the hollow space 58 which is formed between collar59 and annular support 61, there is a coil spring shaped actuator 60 ofmemory metal, whose control and with it the operation of the valvecorresponds to that which was described in connection with the exemplaryembodiment according to FIG. 3.

In FIG. 8, there is provided for a similar purpose an arrangement whichis controllable in a manner similar to

FIG. 4. There, operator 62 for the orifice 11 which is provided at thelevel of bowl housing 2 in bowl lid 8 is not in the form of a slidevalve but is in the form of a hollow cylindrical piston which isslidably located in a hollow space 64 parallel to the centrifuge axis ofrotation. Between the end surface of hollow space 64 adjacent the bowlhousing 2 and its confronting end face of operator 62, there is locatedthe actuator 63 in the form of a coil spring-like memory metal, whereasbetween the end face of hollow space 64,which faces away from bowlsidewall 2, and its confronting face of operator 62, there is located aconventional coil spring 66. In the hollow space 64, there terminates aradially extending channel 67 for supply of the heating medium whichends in an annular space 39 that communicates with the outlet opening ofa supply pipe 15 in previously described manner, so that gaseous orliquid heating medium reaches the hollow space 64 and, through thehollow in the cylindrical piston shaped operator 62 reaches the locationof actuator 63 from where it can be removed through an outlet opening68. The control of the actuator 33 and with it the setting of theannular piston shaped operator 62 takes place in a fashion similar tothat described in connection With FIG. 4. The intended application isalso similar to the explanations given with respect to FIG. 1. Forcooling the actuator there is used the centrifuged material which exitsthrough aperture 11.

In FIG. 9, the sill which is associated with the discharge openings 21for the liquid phase of the mixture to be separated is subdivided intoseparate sill plates 72, which are radially slidable relative to bowllid 6. The sill plates 72 are respectively engaged by the radially outerend of one of the actuators 73 which are tube shaped and variable inlength due to memory metal action. This actuator is supported radiallyinwardly by bowl lid 6 and surrounded by a supply pipe 74. In theradially outer region of the hollow space of tube-like actuator 73 whichserves as control medium channel 76, there is provided a relativelynarrow outlet opening 75, through which the heating or cooling mediumthat flows through the control medium channel 76 via supply pipe 15 andannular space 39 can be removed. When heating medium is supplied and atransformation from martensite into austenite takes place, the tubeshaped actuator 73 becomes shorter so that the corresponding sill platebecomes displaced radially inward. Upon falling below the transformationtemperature, i.e. by supply of an appropriate cooling medium, thistemperature specific shape of the austenite structure is againrelinquished, so that, under centrifugal force or a shock absorberspring (not shown) the tube again radially lengthens, whereby the sillplate assumes a greater inner diameter. In this way it is possible tospecifically regulate from outside the depth of pool 17 in theseparating chamber of the centrifuge as a function of temperature. Here,too, stepwise occurring changes are possible through appropriate seriesor parallel connection of memory metals. If the operation with largesill diameter is to take place only briefly then, for that purpose, theactuator 73 is supplied with cooling medium, while the remainingoperation transforms the memory metal into the austenitic temperaturespecific shape due to the then prevailing operating temperature, therebyreducing the sill diameter.

The exemplary embodiment according to FIG. 10 shows the application ofan actuator 80 made of a coil spring shaped memory metal for relievingthe lubricant pressure during increasing heating and the accompanyingchanging volume and viscosity of the lubricant. The lubricant space 81of helix bearing 7 is provided with seals 82 and terminates - 83 - in ahollow space 78 serving as compensating chamber in which there islocated a piston shaped operator slidable parallel to the axis ofrotation of the centrifuge. The coil spring, shaped actuator 80 islocated in the region of hollow space 78 adjacent to lubricant space 81,i.e. between the end face of hollow space 78 facing the lubricant spaceand the opposing end face of the piston. The remaining hollow spaceportion facing away from that space serves to receive a mechanical coilspring and is provided with exhaust opening 84. The actuator 80 serveshere as sensor for the lubricant temperature, in such a manner that uponexceeding a predetermined threshold and with it a transformation of themartensitic into the austenitic structure, there takes place an increaseof the coil spring shaped memory metal in the lengthwise direction ofits coil shape, whereupon the piston shaped operator 77 is displacedagainst the force of the restoring coil spring, so that the space whichis available for the lubricant also becomes larger. Upon falling of thetemperature and martensite formation which this makes possible, therestoring coil spring 79 again displaces the piston 77 in the directionof a shortening of the coil spring shaped memory metal, so that thehollow space for the lubricant again becomes smaller. In this manner oneinsures that a predetermined temperature of the lubricant must first bereached before an enlargement of the lubricant space takes place, sothat the lubricant which is then more fluid and expanding does notoverload the seals and create leakage. The displacement of the pistoncan take place step-wise through appropriate series or parallelconnections of memory metals, as previously explained in the course ofthe above-mentioned exemplary embodiments. Basically it would also bepossible to connect several pistons in parallel and to equip them withmemory metals having different temperature change values.

The exemplary embodiments previously discussed and illustrated in thedrawings disclose only in part the use of force storage means, orsprings, which cooperate in one way or another with a memory metal. Insome or all of these examples there can be provided force storage means,or springs which urge the memory metals toward their starting shape, inorder to ensure the durability of the shape changing capability. This isadvisable whenever the forces which arise to reinforce the restorationto the starting shape are inadequate for continuous operation, or arenot reliably permanent.

I claim:
 1. Centrifuge for separating substances comprising:at least oneoperable device rotatably located in a rotating region of thecentrifuge, controlled by at least one co-rotating mechanical actuatorfor determining the operation of said at least one device, in which theactuator exhibits a shape change, resulting in at least one temperaturespecific configuration which is controlled by heating and/or cooling,and the actuator is bathed in a liquid or gaseous heating and/or coolingcontrol medium to provide the temperature variation which causes theactuator shape change.
 2. Centrifuge according to claim 1, whereinthetemperature variation needed to cause the shape change of the actuatoris smaller than the temperature range provided by said heating and/orcooling, so that the shape change takes place suddenly.
 3. Centrifugeaccording to claim 1, whereinat least one of the actuators is formedfrom a memory metal.
 4. Centrifuge according to claim 3, whereintheshape change of the memory metal involves a transformation from themartensitic to the austenitic state resulting in movement in onedirection, or a reversion into the martensitic state resulting in returnmovement, and the movement in the one direction takes place against thecentrifugal force exerted by the centrifuge during rotation, while thereturn movement takes place with centrifugal force reinforcement. 5.Centrifuge according to claim 3, whereinthe direction of movement of atleast one of the actuators, upon transformation of the actuator ofmemory metal from the martensitic into the austenitic state is againstthe force of a return spring while the return movement upon reversion ofthe actuator into the martensitic state takes place with spring forcereinforcement.
 6. Centrifuge according to claim 5, whereinat least oneof the actuators of memory metal is a pull rod, a torsion bar, or abending member.
 7. Centrifuge according to claim 5, whereinat least oneof the actuators is also the sensor for temperatures established by thecentrifuge and/or the substances in the centrifuge.
 8. Centrifugeaccording to claim 7, whereinthe temperature change of at least one ofthe actuators takes place upon introduction of cleaning liquid afterprior operation with cold centrifuged medium.
 9. Centrifuge according toclaim 7, whereinthe temperature change of at least one of the at leastone actuator takes place through contact with outflowing centrifugedmedium.
 10. Centrifuge according to claim 7, whereinthe centrifugeincludes a helix having a bearing space filled with lubricant andconstituting a pressure equalization chamber, or being in communicationwith such a chamber, whose internal volume is adapted to be enlarged bymeans of at least one of said actuator in contact with the lubricant inresponse to the lubricant temperature rise, by means of at least onepiston guided within a hollow space, said piston having at one end aface exposed to the lubricant at which there is positioned the actuatorconstituted of at least one coil spring shaped memory metal and saiddistort having at its opposite end a face against which there bears arestoring spring.
 11. Centrifuge according to claim 1, whereinat leastone of the actuators exhibits a repeatable shape change effect, changingfrom an initially stable configuration through cyclic heating andcooling into a different configuration and reverting into the initialconfiguration.
 12. Centrifuge according to claim 1, whereinat least oneof the actuators is formed of two or more memory metals arranged inparallel and/or in series.
 13. Centrifuge according to claim 1,whereinat least one of the actuators is formed of two or more memorymetals connected to each other, positioned in series and/or parallel andhaving shape changes which oppose each other in response to temperatureresponsive phase change.
 14. Centrifuge according to claim 1, whereinatleast one of the controlled devices is a regulating means for openingand closing a nozzle opening, to which regulating means the at least oneactuator is connected.
 15. Centrifuge according to claim 14, whereinthecentrifuge has a bowl having a radially outward region containing thenozzle opening and so arranged that the centrifuge bowl is adapted to beemptied through this nozzle opening.
 16. Centrifuge according to claim14, whereinthe centrifuge has a bowl having a region for containingthick sludge, and the nozzle opening is located in the thick sludgeregion and is so arranged that the thick sludge is adapted toperiodically be emptied from the centrifuge bowl through this nozzleopening.
 17. Centrifuge according to claim 14, whereinthe centrifugebowl contains an overflow sill and the nozzle opening is located at alarger diameter than the overflow sill, so that when the nozzle openingis open there is established an inner diameter of the liquid level whichis greater than the inner diameter determined by the overflow sill. 18.Centrifuge according to claim 14, whereinthe centrifuge bowl contains aseparating chamber and two spaced-apart sill plates, the sill platefacing the separating chamber having a larger inner diameter than theother sill plate, so that when the nozzle opening is opened the innerliquid diameter is determined by the sill plate with the larger innerdiameter and when the nozzle opening is closed, it is determined by thesill plate with the smaller inner diameter.
 19. Centrifuge according toclaim 1, whereinat least one of the actuators consists of a rod orhollow rod whose length is variable as a function of temperature, and isconnected to a sill plate which is radially slidable with respect to adischarge opening.
 20. Centrifuge according to claim 1, which is ascroll conveyor centrifuge.
 21. Centrifuge according to claim 1, whichis a drum centrifuge.
 22. Centrifuge according to claim 1,whichcomprises a spring which provides the force which makes the at least oneactuator assume its respective initial configuration.